One type of labeling panel is known from Federal Republic of Germany Gebrauchsmuster No. 1,894,755. In this known design there are two longitudinal ribs for reinforcement on the back side of the panel which consists of a profiled bar. Pins are inserted at the ends of the longitudinal ribs, lying parallel to the panel. Said pins slide into vertical slots, which, in turn, are positioned in a part of the mounting frame. Thus, the panel can be swivelled in a vertical direction to either of two end settings so that in the lower end setting the panel's lower edge grips the upper edge of the row of plug-in modules which are to be held in place, while in its upper end setting the panel releases the upper edges. In order to be able to fasten the panel in both end settings, the lower slot of the two slots has a reinforced design, and a corresponding pin, which mates with one of the longitudinal ribs, is held in place by a spring in one of the two end settings.